The present invention relates to the testing of semiconductor wafers and, in particular, to establishing electrical connection between the wafer and a wafer chuck.
Semiconductor wafers are often tested both individually and to monitor process conditions. During testing the wafers are typically held by an electrically conductive vacuum chuck. Because the wafers usually have a backside oxide layer, it is usual to scratch through the oxide with a pointed electrode to insure that the bulk semiconductor material within the wafer is electrically connected to the chuck (i.e., an ohmic connection). It is often difficult to both successfully make this connection and to determine if indeed it was successful.
U.S. Pat. No. 5,498,974 shows the use of a Kelvin probe to make measurements on a semiconductor wafer mounted on a vacuum chuck and is incorporated herein by reference.